This invention lies in the field of badge and document reading devices and, more particularly, devices for reading encoded data and communicating with other remote electronic data processing apparatus.
The rapidly expanding data processing technology has forced the development of many new modes of data collection. One such method which is currently increasing and has a large potential for industrial application is that of collecting data from badges or the like which are carried by individuals. In many industrial systems, activity records and other events are monitored by having individuals at predetermined locations insert badges into readers to record specified events, which badges are designed to be encoded so as to permit reliable data recognition. The types of such badges are standardized, and for each such type a predetermined amount of information in a given format is available. The badge reader may have a motorized transport system or, as in many cases where it is either impractical or undesirable to have such a motorized transport system within a small reader the person who carries the badge inserts it manually and then withdraws it after the reader performs the reading operation.
The reader having obtained the desired information from the badge or other document, the following task is to communicate such information in a desired form to a central computer or other remote piece of equipment within an overall data processing system. For the reader disclosed herein, data transfer as such is essentially one-way, the data which has been read from the badge or other document being transmitted to the remote location. However, overall communication must be two-way, since the computer must send certain logic signals to the card reader for control thereof, meaning that the card reader must be adapted to receive and process given messages from the external location. Control of transmission from the reader to the remote location, and of reception of messages from the remote location by the reader, is organized around a clock generator, which establishes the basic timing for data processing within the reader and for controlling transmission in either direction. In systems of this sort, two general approaches are available, namely (1) keep the basic clock generator going at all times and gate clock signals as desired or (2) enable the clock generator only when desired. The second approach presents the opportunity to substantially simplify gating circuitry, but requires a highly accurate means of turn-on and turn-off of the basic clock generator, in order to achieve the precise timing which is required every time the clock is turned on. The timing control circuitry disclosed and claimed herein provides a reliable on-off control of the clock generator and corresponding control of the transmit-receive operations of the badge reader.